1 Technical Field of the Invention
This disclosure relates generally to a rotating pumping apparatus with a sealing mechanism in which a sealing member made of up a resinous ring and a rubber ring is disposed in a clearance between a pump housing and a shaft extending in the pump housing, and the resinous ring is placed in close contact with the shaft to create a hermetic seal.
2 Background Art
Japanese Patent First Publication No. 2012-063003 teaches a rotating pump with a sealing assembly for creating a hermetical seal between a housing and a shaft disposed inside the housing. The sealing assembly is made up of a resinous ring and a rubber ring. The rubber ring is disposed outside the resinous ring and works to elastically urge the resinous ring against the shaft to create the hermetical seal between the housing and the shaft, thereby blocking the leak of brake fluid from a pump through a gap between the housing and the shaft. The rotating pump also has an oil seal which constructs a double seal mechanism along with the sealing assembly of the resinous ring and the rubber ring. The oil seal is located farther away from the pump than the sealing assembly is.
When the pressure of the brake fluid present between the pump and the sealing assembly is elevated by the operation of the pump, so that the brake fluid leaks through the sealing assembly, the double seal mechanism serves to hold the brake fluid within a chamber between the sealing assembly and the oil seal. When the pressure of the brake fluid within the chamber drops at the end of the operation of the pump, the brake fluid returns back to the pump through a gap on the outer periphery of the sealing assembly, that is, between the rubber ring and the housing.
There is, however, a possibility that grease between the oil seal and the shaft may leak following the brake fluid returning from the chamber between the sealing assembly and the oil seal toward the pump and then enter a brake fluid circuit. Particularly, in the case where the rotating pump primes the brake fluid and supplies it to a wheel cylinder to elevate the pressure in the wheel cylinder, the rotating pump needs to be operated for a long time, thus increasing the possibility of leakage of the grease into the brake fluid circuit.